The biogenesis of mitochondria in Baker's yeast will be examined. Particular emphasis will be placed on: 1. Control of the replication and continuity of the mitochondrial genome. 2. An assessment of the function, characterization, and the processing of products of mitochondrial protein synthesis. 3. Translational compartmentation related to mitochondrial assembly. 4. Mitochondrial division. Studies will take advantage of cold sensitive mutants isolated in this laboratory which are conditionally defective in mitochondrial function or continuity. We plan to look at the relationship between mitochondrial membrane proteins and mitochondrial DNA replication by techniques to specifically label mitochondrial DNA and products of mitochondrial protein synthesis. Biochemical and electron microscopic studies will be carried out to characterize the functional properties of a class of 80 ribosomes associated with yeast mitochondria. Attempts will be made to alter mitochondrial division in yeast by the electron transport inhibitor, Antimycin A.